Is cavity wall insulation right for me?
Guide to Wall Insulation
Up to half of the heat loss from a house occurs through the walls. This can be reduced by two-thirds by insulating the walls.
Most houses built before about 1980 have no wall insulation. Many (though not all) houses built during the 1980s have some wall insulation. Houses built since the 1991 Building Regulations came into effect are required to have wall insulation.
Insulation may be placed on the outside, in the cavity or on the inside of a wall, without altering the overall insulation properties.
When considering wall insulation, first you should find out whether your house has cavity walls or solid walls. A building contractor, BER Assessor or architect will be able to tell you if you have cavity walls in your new or older house.
Cavity wall insulation
The walls of many houses consist of two ‘leaves’ of brick or concrete block with a cavity or space between them to resist rain penetration.
In older houses insulation can be injected into this cavity through holes drilled through the outer leaf, by means of a blowing or pumping machine.
Since the work is done from outside, it cause minimum disturbances inside. The drilled holes, which are typically about 25mm (1 inch) in diameter and spaced a metre or so apart, are then filled to match the wall appearance as closely as possible. The job typically takes less than a day.
In relation to the pumping of your walls with a bonded bead system you would noticeably improve the overall thermal properties of your house and in turn reduce your energy bills for the winter months.
Suitability of Cavity Insulation
It is important before deciding to insulate existing cavity walls that you check their suitability for cavity insulation. This assessment will take account of the degree of exposure of the house to wind-driven rain and the construction details and condition of the walls. Any ventilation openings in the wall will also be checked to ensure that these will not be blocked by the insulation.
There are a number of issues you should be aware when filling your wall’s cavity:
If there were any frost or structural damage to any of the house’s external walls pumping of beads into the cavity would not be advised.
The width of the cavity between your external wall leaf and the installed aero-board should be at least 50mm.
If there is any problem with dampness in the internal leaf it would not be recommended to add the beads to the cavity as they would only increase the path for water to travel into the wall.
If the wall suffers from rain penetration at times, this problem must be remedied first.
In some cases, the walls may be found to be unsuitable for cavity insulation or may require some remedial work beforehand.
Savings
The cost of cavity wall insulation depends on a number of factors, including the width of the cavity, but it is typically in the region of €5 to €7 per square metre. For a typical semi-detached house, this gives a total cost of about €550-€700. With annual fuel savings of €200 to €320, the payback period will be in the region of 4 to 7 years.
You may be able to negotiate a lower price if you can persuade some of your neighbours to have their walls insulated at the same time.
Hi
Can you comment on the best course of action with hollow block building? This will be the blight of the nation when it comes to insulating our homes. To look at dry lining would cost an absolute fortune, not to mention re-decorating. The government grants don’t go far towards this.
What are the options for people in this situation (and there are a lot of them)? And are they really worth it, as you say more modern houses (even if they are hollow block) will still have some kind of wall insulation.
Thanks!
Are there any recycling facilities avavilable in ireland for the various types of thermal wall insulation?
For the majority of homes having cavity wall insulation installed makes a graet deal of sense. As well as the obvious environmental benefits it will, as you say, pretty much pay for itself within a few years.
You can also get a grant of 400 euro from SEI under the “Home Energy Saving Scheme”. For most houses with a decent cavity this brings the payback period down to just a few short years.
“Andrea Carroll says:
July 24, 2009 at 2:18 am
Hi
Can you comment on the best course of action with hollow block building? This will be the blight of the nation when it comes to insulating our homes. To look at dry lining would cost an absolute fortune, not to mention re-decorating. The government grants don’t go far towards this.”
Andrea, your question is highly pertinent given the huge number of houses built with hollow block in Ireland. I understand that External insulation is the best option in this case (hollow block). SEI are offering grants up to €4000 for external insulation. You could check articles written by Joseph Little for Construct Ireland magazine arguing that dry lining ‘creates an hygrothermically unstable condition and a propensity for mould‘. To avoid this problem, the internal insulation should be so thick that you would probably loose valuable floor area in your home.
Apart from insulation it is also important to consider natural ventilation in winter time; the extra insulation will impede adequate ventilation, in which case it can be addressed with a passive stack ventilation system or a Mechanical heat recovery ventilation system.
You are right here in relation to lack of support; there are no grants for ventilation measures.
Should the government impose a mandatory regulation in which building contractors can only insulate a home with energy saving approved insulation types. I mean styrofoam should be banned at this stage! yes? no?